The chromosomes then climb along the spindle like a mountain climber goes up ropes.

Why is this called a spindle?
Recall from history class – a spindle is a disk-shaped tool, with a hole in the center, used to spin threads into cloth.
When biologists first discovered this, it reminded them of this.

How do the chromosomes climb along this spindle?
Like how mountaineers climb up a rope.

Mountaineers use metal anchors to dig into a rock wall,
attach ropes with a carabiner, and climb up the wall.

Chromosome (mountaineer) use a kinetochore (carabiner) to attach to the spindle apparatus (rope) to move up the cell (mountain.)

Learning Standards

HS-LS1-4. Construct an explanation using evidence for why the cell cycle is necessary for the growth, maintenance, and repair of multicellular organisms. Model the major events of the cell cycle, including (a) cell growth and DNA replication, (b) separation of chromosomes (mitosis), and (c) separation of cell contents.

Disciplinary Core Idea Progression Matrix: “In multicellular organisms, the processes of mitosis and differentiation drive an organism’s growth and development. Each chromosome pair contains two variants of each gene. Offspring that result from sexual reproduction inherit one set of chromosomes from each parent”